The present invention relates generally to the field of robotics and specifically to robotic tool coupling device to prevent damage in the event of a crash event.
Robots are widely utilized in industrial assembly line applications to perform repetitive tasks very precisely without the need for human operation, interaction, or supervision. For example, robots are commonly used in the automotive industry to perform a number of tasks such as material handling and spot-welding of automobile bodies.
To amortize the considerable cost of an industrial robot over a variety of tasks, the robot arm is typically separate from a diverse array of tools, which are removably attached to the end of the robot arm. Occasionally, a robotic tool may encounter unexpected obstacles in the production line environment. If the robotic tool impacts the obstacle with sufficient force, or if the robot continues to move once the tool has come into contact with the obstacle, the robotic tool or the robot arm itself may become damaged. Additionally, a robotic tool may exert or encounter a torque force with respect to the robot arm that exceeds safe limits, also causing damage.
In order to avoid this undesirable result, a crash protection device may be connected between the robot arm and the robotic tool. The crash protection device senses the degree of force between the robot arm and the robotic tool, and signals a controller (that may be associated with the robot arm, the robotic tool, both, or some other system component) of the impact or excess torque condition, collectively referred to herein as a xe2x80x9ccrash condition.xe2x80x9d The controller may then shut down the robotic tool, halt further movement of the robotic arm, trigger an alarm, or take other relevant action.
Considering the wide variety of tasks the robot may be programmed to perform, and the great diversity of robotic tools available for attachment to it, it is difficult or impossible to accurately predict a single threshold force or torque that should trigger a crash event. In some applications, some degree of force or torque between the robot arm and the robotic tool may be desirable or even unavoidable; in other applications, the same degree of force should trigger a crash signal to the controller. To accommodate a variety of applications, a crash protection device may be designed to xe2x80x9cgivexe2x80x9d or flex, thus providing the tool with a limited amount of freedom of movement when it encounters an obstacle or exerts a torque. This flexibility is referred to as xe2x80x9ccompliance.xe2x80x9d Preferably, the degree of compliance in a robot crash protection device is variable, and more preferably, it can be adjusted without disassembly of the device.
Because an obstacle can exert different forces on the robotic tool depending upon where the two come into contact, it is desirable for a crash protection device to provide compliance in several directions (e.g., in the x, y, and z directions, as well as rotationally). Additionally, because the environments in which robots are used are sometimes hostile and unsafe for humans, it is also desirable for the crash protection device to be capable of automatically returning to its original position, or xe2x80x9cresetting,xe2x80x9d when the overload condition no longer exists, without the need for human intervention. Thus, it is desirable to provide a crash protection device capable of resetting itself, regardless of whether the overload condition was due to linear or rotational movement.
Compliance in a plurality of directions normally means that two or more sensors are required to detect an overload condition, since displacement of the crash protection device can occur in a variety of directions. Each additional sensor, however, adds additional expense to the crash protection device. Thus, it is desirable to provide a crash protection device that exhibits compliance in a plurality of directions, but requires only one sensor to detect an overload condition.
The present invention relates to a robotic crash protection device adapted to be interposed between a robot arm and a robotic tool for detecting a crash. The device includes a housing, a piston having a generally central bore movably mounted within the housing, an actuator for engaging the piston and moving the piston in response to a crash, and a switch disposed within the housing and generally aligned with the bore of the piston. The switch has a pair of contacts operative to move between open and closed positions. The contacts are disposed such that in one position the bore of the piston engages the contacts and maintains the contacts in a closed position and in another position the bore of the piston permits the contacts to assume an open position.
In another aspect, the present invention relates to an electrical sensor for a robotic crash protection device. The sensor includes a switch disposed within the robotic crash protection device, the switch including two contacts, each of which includes an engagement surface. The sensor also includes a dielectric annular collar, and an adjustment screw threadedly connected to the switch and operative to alter the axial position of the switch with respect to the collar. The switch is actuated to a first state when the engagement surfaces are confined within the collar in a default condition of the robotic crash protection device, and the switch is actuated to a second state by the engagement surfaces moving outside of the collar in response to a robotic tool crash that transitions the robotic crash protection device out of the default condition.